1. Field of the Invention
The present invention is directed in general to mechanical movements, and more particularly to an actuating mechanism adapted for use in association with rotatably mounted adjusting shafts such as are employed in, for instance, optical instruments.
2. Prior Art
There are numerous types of adjusting mechanisms used in optical instruments which vary from a single shaft and knob assembly to coaxially mounted multi-shaft and knob assemblies. The single shaft and knob assemblies are generally used on inexpensive instruments, whereas the coaxially mounted assemblies are found on more sophisticated and expensive instruments. The single shaft and knob only permits adjustment which is directly proportional to the amount of rotation. The multi-shaft coaxial assembly allows for a coarse adjustment and a fine adjustment. In some instances, such as may be seen in U.S. Pat. No. 4,173,902, a further knob may be incoporated which would provide an adjustment which is intermediate to the available coarse and fine adjustments.
In systems such as these however, it is necessary that the operator first rotate one knob and then move the hand from that knob to a second knob. Quite frequently, the adjusting knobs are situated on the instrument in a location which is less than ideal from the standpoint of operator comfort and accessability. For instance, viewing aerial photography at high magnification require frequent focus adjustments. Accordingly, the operator must continually move his or her hand back and forth from a rest surface to the focus adjust knobs. This can be quite annoying, and in some instances of prolonged useage, very tiring.
In an attempt to alleviate this type of difficulty some instrument makers resorted to mounting a lever to at least one of the focus knobs, such as is seen in previously mentioned U.S. Pat. No. 4,173,902. The lever extends from the knob generally toward the operator so that it may easily be grasped and rotated. However, in applications such as these the lever also rotates when the knob is rotated and therefore becomes obtrusive.
A further example of a microscope monoaxial coarse/fine mechanism which features an adjusting lever may be seen in U.S. Ser. No. 385,734, entitled "A Microscope Fine Focus Control Mechanism" and filed on June 7, 1982 by inventor J. A. Clark, co-applicant of the instant invention. In this device, the lever is affixed to a hub which is mounted via a tapered bushing to the coarse shaft. The tapered bushing is eccentrically mounted to the instrument. The hub and lever remain stationary when the coarse shaft is rotated. However, rotating the lever induces the hub to also rotate. As the hub is eccentric, rotation of it will cause the coarse shaft to be vertically offset which in turn translates to a vertical adjustment of the microscope objective.